Re-doped Ti4O7 anode and preparation method thereof

Abstract

The application discloses a Re-doped Ti4O7 anode and a preparation method thereof, relates to the technical field of electrochemical technology for repairing polluted water bodies, and comprises the following steps: adding an ammonium perrhenate solution into a tetrabutyl titanate solution, adding an ethanol aqueous solution, continuously stirring, and standing to obtain a gel; grinding the gel into a powder after drying, and calcining to obtain Re-doped TiO2; adding the Re-doped TiO2 and carbon black into anhydrous ethanol, dispersing and ball-milling, vacuum drying, and performing carbon reduction treatment to obtain Re-doped Ti4O7; performing discharge plasma sintering on the Re-doped Ti4O7, naturally cooling, and obtaining the Re-doped Ti4O7 anode; adding modified carbon nanotubes into deionized water, ultrasonic dispersing, adding the Re-doped Ti4O7 anode, vacuum impregnating, drying, heat treating, and obtaining a composite Re-doped Ti4O7 anode.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology for the remediation of polluted water bodies, specifically a Re-doped Ti4O7 anode and its preparation method. Background Technology

[0002] Polyfluorinated and perfluorinated compounds (PFAS) are a class of synthetic chemicals composed of a hydrophobic fluorinated alkyl chain at one end and a hydrophilic functional group at the other. These compounds are not only hydrophobic and oleophobic but also chemically stable, and are widely used in industrial production and daily life. Industrial wastewater discharge is one of the main sources of PFAS pollution in aquatic environments; however, traditional wastewater treatment processes are ineffective in removing PFAS.

[0003] Current research indicates that electrochemical oxidation is an effective method for degrading PFAS. There are two main pathways for the electrochemical oxidation degradation of perfluorinated compounds: one is through hydroxyl radicals generated on the anode surface entering the water and transferring electrons to the pollutants; the other is through direct electron transfer at the anode, resulting in degradation of the pollutants.

[0004] Ti4O7 exhibits high electrical conductivity and oxygen evolution potential, good corrosion resistance, and low preparation cost. Using Ti4O7 as an anode for the electrochemical oxidation degradation of PFAS in complex water bodies is currently one of the most effective methods. However, pure Ti4O7 has drawbacks such as a lower interfacial charge transfer rate and lower ·OH yield compared to traditional inactive anode materials.

[0005] Therefore, developing a novel anode, Ti4O7, is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a Re-doped Ti4O7 anode and its preparation method to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a Re-doped Ti4O7 anode includes the following steps: S1: Add ammonium perrhenate solution to tetrabutyl titanate solution, add aqueous ethanol solution, continue stirring, let stand, and obtain gel; S2: The gel is dried, ground into powder, and calcined to obtain Re-doped TiO2; S3: Add Re-doped TiO2 and carbon black to anhydrous ethanol, disperse and ball-mill, vacuum dry, and perform carbon reduction treatment to obtain Re-doped Ti4O7; S4: Re-doped Ti4O7 is subjected to discharge plasma sintering and natural cooling to obtain a Re-doped Ti4O7 anode; S5: Modified carbon nanotubes were added to deionized water, ultrasonically dispersed, and then Re-doped Ti4O7 anodes were added. The mixture was then vacuum impregnated, dried, and heat-treated to obtain a composite Re-doped Ti4O7 anode.

[0008] Further, in step S1, the preparation process of the ammonium perrhenate solution is as follows: add the ammonium perrhenate aqueous solution to ethanol and mix evenly to obtain the ammonium perrhenate solution; the preparation process of the tetrabutyl titanate solution is as follows: add tetrabutyl titanate to ethanol and mix evenly to obtain the tetrabutyl titanate solution. In the preparation of ammonium perrhenate solution, the mass ratio of ammonium perrhenate aqueous solution to ethanol is 1:(1-10), and the rhenium content in the ammonium perrhenate aqueous solution is 0-10%. In the preparation of tetrabutyl titanate solution, the mass ratio of tetrabutyl titanate to ethanol is 1:(1-10); The ethanol-water solution is composed of ethanol and deionized water, with a mass ratio of ethanol to deionized water of (1-10):1.

[0009] Further, in step S1, the mass ratio of ammonium perrhenate solution, tetrabutyl titanate solution and aqueous ethanol solution is 1:1:(1-10).

[0010] Further, in step S2, the calcination parameters are: the gas atmosphere is air, the heating rate is 3-10℃ / min, the maximum temperature is 500-600℃, and the calcination time is 1-4h.

[0011] Further, in step S3, the carbon reduction process parameters are as follows: the gas atmosphere is argon, the argon flow rate is 80-100 mL / min, the heating rate is 5-10 ℃ / min, the maximum temperature is 1000-1200 ℃, and the holding time is 80-160 min. The molar ratio of Re-doped TiO2 to carbon black is (4-5):1.

[0012] Further, in step S4, the discharge plasma sintering parameters are: sintering pressure of 3-8 MPa, heating rate of 50-60℃ / min, maximum sintering temperature of 1000-1200℃, and sintering time of 10-30 min.

[0013] Further, in step S5, the preparation process of the modified carbon nanotubes is as follows: carbon nanotubes are placed in concentrated nitric acid, refluxed at 80-110℃ for 3-8 hours, cooled to room temperature, washed and dried to obtain pretreated carbon nanotubes; Pretreated carbon nanotubes were added to deionized water, ultrasonically mixed, heated to 70-80℃, and tin chloride pentahydrate and antimony chloride were added. The mixture was stirred, and the pH was adjusted to 10 with sodium hydroxide. The mixture was washed, filtered, vacuum dried, and calcined under nitrogen protection to obtain modified carbon nanotubes.

[0014] Furthermore, in the preparation process of the pretreated carbon nanotubes, the mass ratio of carbon nanotubes to concentrated nitric acid is 1:(20-50); in the preparation process of the modified carbon nanotubes, the mass ratio of pretreated carbon nanotubes, tin chloride pentahydrate, and antimony chloride is 1:(3-8):(0.1-0.4).

[0015] Further, in step S5, the vacuum impregnation time is 1-3 hours; the heat treatment parameters are as follows: the gas atmosphere is an inert gas, the heating rate is 3-10℃, the maximum temperature is 200-300℃, and the time is 1-2 hours; the mass ratio of modified carbon nanotubes to Re-doped Ti4O7 anode is 1:(10-20).

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces metallic Re into Ti4O7. On the one hand, metallic Re can... 7+ The valence state exists in Ti4O7, replacing part of Ti. 4+ This generates lattice defects, oxygen vacancies, and charge carriers, significantly enhancing the interfacial charge transfer rate of Ti4O7 and promoting direct electron transfer processes occurring at the electrode surface. On the other hand, Re... 7+ The high valence state of Ti4O7 facilitates the adsorption of PFAS onto the electrode through electrostatic interactions, thereby improving mass transfer efficiency and significantly enhancing the catalytic activity of Ti4O7 anode for PFAS. This is beneficial for promoting the application of Ti4O7 in the treatment of PFAS in fluorochemical wastewater.

[0017] 2. This invention employs spark plasma sintering (SPCS) technology to prepare Ti4O7 anodes. On one hand, it effectively prevents excessive growth of Ti4O7 grains, maintains a fine-grained structure, and improves the electrochemical surface activity of the Ti4O7 anode; on the other hand, it effectively reduces the volatilization and segregation of metallic Re, promotes the uniformity of Re doping, reduces charge transfer resistance, and promotes direct electron transfer at the electrode.

[0018] 3. This invention introduces modified carbon nanotubes into the Ti4O7 anode. First, the carbon nanotubes are pretreated with a mixture of sulfuric acid and nitric acid to introduce oxygen-containing groups such as hydroxyl and carboxyl groups, which is beneficial for subsequent loading of antimony-doped tin oxide and enhances the interfacial bonding between the carbon nanotubes and the Ti4O7 anode. Second, antimony-doped tin oxide modifies the surface of the carbon nanotubes. On the one hand, it improves the corrosion resistance of the carbon nanotubes in fluorochemical wastewater; on the other hand, it further enhances the conductivity and surface catalytic activity of the Ti4O7 anode, promotes the exposure of active sites and interfacial charge transfer, and thus synergistically enhances the direct electron transfer process and ·OH production of the Ti4O7 anode with the doped metal Re. Attached Figure Description

[0019] Figure 1XPS spectra of Embodiment 1 and Comparative Example 1 of the present invention; Figure 2 This is an EIS schematic diagram of Embodiment 1 and Comparative Example 1 of the present invention; Figure 3 This is a schematic diagram comparing Cdl of Embodiments 1-3 and Comparative Example 1 of the present invention; Figure 4 This is a schematic diagram comparing the oxalic acid degradation capabilities of Example 1 and Comparative Example 1 of the present invention. Figure 5 This is a schematic diagram comparing the salicylic acid degradation capabilities of Example 1 and Comparative Example 1 of the present invention. Figure 6 This is a schematic diagram comparing the coumarin degradation capabilities of Example 1 and Comparative Example 1 of the present invention. Figure 7 This is a schematic diagram comparing the perfluorooctanoic acid (PFOA) degradation capabilities of Example 1 and Comparative Example 1 of the present invention. Figure 8 This is a schematic diagram showing the defluorination rate of perfluorooctanoic acid in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the following examples, the diameter of the carbon nanotubes is 20 nm.

[0022] Example 1: A method for preparing a Re-doped Ti4O7 anode: S1: According to the molar ratio of titanium to rhenium of 97:3, 0.122g of ammonium perrhenate was added to a mixture of 1ml deionized water and 5ml ethanol and mixed evenly to obtain an ammonium perrhenate solution; 5ml of tetrabutyl titanate and 30ml of ethanol were mixed evenly to obtain a tetrabutyl titanate solution; 20ml of ethanol and 4ml of deionized water were mixed evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 8g of aqueous ethanol solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain Re-doped TiO2; S4: 4 mol of Re-doped TiO2 and 1 mol of carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and held at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Re-doped Ti4O7. S5: Discharge plasma sintering of Re-doped Ti4O7 was carried out under the following conditions: heating to 1100℃ at a rate of 50℃ / min under a sintering pressure of 5MPa, sintering at 1100℃ for 20min, and then naturally cooling to obtain the Re-doped Ti4O7 anode.

[0023] Example 2: A method for preparing a Re-doped Ti4O7 anode: S1: According to the molar ratio of titanium to rhenium of 95:5, 0.208g of ammonium perrhenate was added to a mixture of 1ml deionized water and 5ml ethanol and mixed evenly to obtain an ammonium perrhenate solution; 5ml of tetrabutyl titanate and 30ml of ethanol were mixed evenly to obtain a tetrabutyl titanate solution; 20ml of ethanol and 4ml of deionized water were mixed evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 10g of ethanol aqueous solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain Re-doped TiO2; S4: 5 mol of Re-doped TiO2 and 1 mol of carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and held at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Re-doped Ti4O7. S5: Re-doped Ti4O7 was subjected to discharge plasma sintering. The temperature was increased to 1100℃ at a rate of 50℃ / min under a sintering pressure of 5MPa, and sintered at 1100℃ for 20min. After natural cooling, Re-doped Ti4O7 anode was obtained.

[0024] Example 3: A method for preparing a Re-doped Ti4O7 anode: S1: According to the molar ratio of titanium to rhenium of 90:10, 0.438g of ammonium perrhenate was added to a mixture of 1ml deionized water and 5ml ethanol and mixed evenly to obtain an ammonium perrhenate solution; 5ml of tetrabutyl titanate and 30ml of ethanol were mixed evenly to obtain a tetrabutyl titanate solution; 20ml of ethanol and 4ml of deionized water were mixed evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 10g of ethanol aqueous solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain Re-doped TiO2; S4: 6 mol of Re-doped TiO2 and 1 mol of carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and held at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Re-doped Ti4O7. S5: Re-doped Ti4O7 was subjected to discharge plasma sintering. The temperature was increased to 1100℃ at a rate of 50℃ / min under a sintering pressure of 5MPa, and sintered at 1100℃ for 20min. After natural cooling, Re-doped Ti4O7 anode was obtained.

[0025] Example 4: A method for preparing a Re-doped Ti4O7 anode: S1: According to the molar ratio of titanium to rhenium of 90:10, 0.438g of ammonium perrhenate was added to a mixture of 1ml deionized water and 5ml ethanol and mixed evenly to obtain an ammonium perrhenate solution; 5ml of tetrabutyl titanate and 30ml of ethanol were mixed evenly to obtain a tetrabutyl titanate solution; 20ml of ethanol and 4ml of deionized water were mixed evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 10g of ethanol aqueous solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain Re-doped TiO2; S4: 6 mol of Re-doped TiO2 and 1 mol of carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and held at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Re-doped Ti4O7. S5: Re-doped Ti4O7 was subjected to discharge plasma sintering. Under a sintering pressure of 5 MPa, the temperature was increased to 1100℃ at a rate of 50℃ / min, and sintered at 1100℃ for 20 min. After natural cooling, Re-doped Ti4O7 anode was obtained. S6: Place 1g of carbon nanotubes in 30ml of concentrated nitric acid, reflux at 80℃ for 4h, cool to room temperature, wash and dry to obtain pretreated carbon nanotubes. S7: Add 1g of pretreated carbon nanotubes to deionized water, mix ultrasonically, heat to 80℃, add 3g of tin chloride pentahydrate and 0.1g of antimony chloride, stir, adjust the pH to 10 with sodium hydroxide, wash and filter, vacuum dry, and calcine under nitrogen protection to obtain modified carbon nanotubes. S8: Add 1g of modified carbon nanotubes to deionized water, disperse ultrasonically, add 10g of Re-doped Ti4O7 anode, vacuum, vacuum impregnate for 2h, heat treat for 2h under nitrogen protection by raising the temperature from 5℃ to 300℃, and obtain composite Re-doped Ti4O7 anode.

[0026] Example 5: A method for preparing a Re-doped Ti4O7 anode: S1: According to the molar ratio of titanium to rhenium of 90:10, 0.438g of ammonium perrhenate was added to a mixture of 1ml deionized water and 5ml ethanol and mixed evenly to obtain an ammonium perrhenate solution; 5ml of tetrabutyl titanate and 30ml of ethanol were mixed evenly to obtain a tetrabutyl titanate solution; 20ml of ethanol and 4ml of deionized water were mixed evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 10g of ethanol aqueous solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain Re-doped TiO2; S4: 6 mol of Re-doped TiO2 and 1 mol of carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and held at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Re-doped Ti4O7. S5: Re-doped Ti4O7 was subjected to discharge plasma sintering. Under a sintering pressure of 5 MPa, the temperature was increased to 1100℃ at a rate of 50℃ / min, and sintered at 1100℃ for 20 min. After natural cooling, Re-doped Ti4O7 anode was obtained. S6: Place 1g of carbon nanotubes in 30ml of concentrated nitric acid, reflux at 80℃ for 4h, cool to room temperature, wash and dry to obtain pretreated carbon nanotubes. S7: Add 1g of pretreated carbon nanotubes to deionized water, mix ultrasonically, heat to 80℃, add 4g of tin chloride pentahydrate and 0.2g of antimony chloride, stir, adjust the pH to 10 with sodium hydroxide, wash and filter, vacuum dry, and calcine under nitrogen protection to obtain modified carbon nanotubes. S8: Add 1g of modified carbon nanotubes to deionized water, disperse ultrasonically, add 15g of Re-doped Ti4O7 anode, vacuum, vacuum impregnate for 2h, heat treat for 2h under nitrogen protection by raising the temperature from 5℃ to 300℃, and obtain composite Re-doped Ti4O7 anode.

[0027] Example 6: A method for preparing a Re-doped Ti4O7 anode: S1: According to the molar ratio of titanium to rhenium of 90:10, 0.438g of ammonium perrhenate was added to a mixture of 1ml deionized water and 5ml ethanol and mixed evenly to obtain an ammonium perrhenate solution; 5ml of tetrabutyl titanate and 30ml of ethanol were mixed evenly to obtain a tetrabutyl titanate solution; 20ml of ethanol and 4ml of deionized water were mixed evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 10g of ethanol aqueous solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain Re-doped TiO2; S4: 6 mol of Re-doped TiO2 and 1 mol of carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and held at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Re-doped Ti4O7. S5: Re-doped Ti4O7 was subjected to discharge plasma sintering. Under a sintering pressure of 5 MPa, the temperature was increased to 1100℃ at a rate of 50℃ / min, and sintered at 1100℃ for 20 min. After natural cooling, Re-doped Ti4O7 anode was obtained. S6: Place 1g of carbon nanotubes in 30ml of concentrated nitric acid, reflux at 80℃ for 4h, cool to room temperature, wash and dry to obtain pretreated carbon nanotubes. S7: Add 1g of pretreated carbon nanotubes to deionized water, mix ultrasonically, heat to 80℃, add 5g of tin chloride pentahydrate and 0.3g of antimony chloride, stir, adjust the pH to 10 with sodium hydroxide, wash and filter, vacuum dry, and calcine under nitrogen protection to obtain modified carbon nanotubes. S8: Add 1g of modified carbon nanotubes to deionized water, disperse ultrasonically, add 18g of Re-doped Ti4O7 anode, vacuum, vacuum impregnate for 2h, heat treat for 2h under nitrogen protection by raising the temperature from 5℃ to 300℃, and obtain composite Re-doped Ti4O7 anode.

[0028] Comparative Example 1: A method for preparing a Re-doped Ti4O7 anode: S1: Mix 1 ml of deionized water and 5 ml of ethanol evenly to obtain a perrhenate-free ammonium solution; mix 5 ml of tetrabutyl titanate and 30 ml of ethanol evenly to obtain a tetrabutyl titanate solution; mix 20 ml of ethanol and 4 ml of deionized water evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 10g of ethanol aqueous solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain TiO2; S4: 6 mol TiO2 and 1 mol carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and kept at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Ti4O7. S5: Ti4O7 was subjected to discharge plasma sintering. The temperature was increased to 1100℃ at a rate of 50℃ / min under a sintering pressure of 5MPa, and sintered at 1100℃ for 20min. After natural cooling, Ti4O7 anode was obtained.

[0029] Comparative Example 2: A method for preparing a Re-doped Ti4O7 anode: S5: Add 0.5g of polyvinyl alcohol to 10g of Re-doped Ti4O7, heat to 1250℃ at a rate of 5℃ / min under a hydrogen-argon mixed gas, sinter at 1250℃ for 4h, and cool with the furnace to obtain a Re-doped Ti4O7 anode. The remaining steps are the same as in Example 3.

[0030] Comparative Example 3: A method for preparing a Re-doped Ti4O7 anode: S1: According to the molar ratio of titanium to rhenium of 90:10, 0.438g of ammonium perrhenate was added to a mixture of 1ml deionized water and 5ml ethanol and mixed evenly to obtain an ammonium perrhenate solution; 5ml of tetrabutyl titanate and 30ml of ethanol were mixed evenly to obtain a tetrabutyl titanate solution; 20ml of ethanol and 4ml of deionized water were mixed evenly to obtain an ethanol-water solution; S2: Add 1g of ammonium perrhenate solution to 1g of tetrabutyl titanate solution, add 10g of ethanol aqueous solution, stir continuously for 3h, let stand for 12h, and obtain gel; S3: After drying the gel, grind it into powder, heat it to 600℃ in air at a heating rate of 5℃ / min, and calcine it for 2h to obtain Re-doped TiO2; S4: 6 mol of Re-doped TiO2 and 1 mol of carbon black were added to anhydrous ethanol, dispersed and ball-milled for 8 h, vacuum dried at 60 °C for 8 h, heated to 1100 °C at 8 °C / min under an argon atmosphere with a flow rate of 80 mL / min, and held at the temperature for 120 min for reduction reaction. The mixture was then naturally cooled to room temperature to obtain Re-doped Ti4O7. S5: Re-doped Ti4O7 was subjected to discharge plasma sintering. Under a sintering pressure of 5 MPa, the temperature was increased to 1100℃ at a rate of 50℃ / min, and sintered at 1100℃ for 20 min. After natural cooling, Re-doped Ti4O7 anode was obtained. S6: Add 1g of carbon nanotubes to deionized water, disperse ultrasonically, add 18g of Re-doped Ti4O7 anode, vacuum, vacuum impregnate for 2h, heat-treat at 5℃ to 300℃ for 2h under nitrogen protection to obtain composite Re-doped Ti4O7 anode.

[0031] Testing: The Re-doped Ti4O7 anode samples prepared in the above examples and comparative examples were subjected to the following tests.

[0032] XPS spectral analysis: The elemental composition of the Ti4O7 anode sample was analyzed using an X-ray photoelectron spectrometer. The test conditions were: Al target, Kα ray source, and fine spectra of titanium, oxygen, and rhenium were analyzed.

[0033] EIS spectrum analysis: A Re-doped Ti4O7 anode was used as the working electrode, a platinum disc as the counter electrode, and a silver-silver chloride electrode (Ag / AgCl) as the reference electrode. The reactant was 0.01 M potassium ferrocyanide (K4[Fe(CN)6]), and the supporting electrolyte was 0.1 M Na2SO4 solution. EIS measurements were performed at open-circuit voltage, with a frequency range of 0.1-10 Hz. 5 The frequency is Hz, and the amplitude is 5 mV. Data is collected and equivalent circuit fitting is performed.

[0034] Double-layer capacitance detection: Using Re-doped Ti4O7 anode as the working electrode, platinum metal disc as the counter electrode, and silver-silver chloride electrode (Ag / AgCl) as the reference electrode, with 0.5 M Na2SO4 solution as the supporting electrolyte, CV curves were measured in the range of 0.6 V to 0.8 V and at scan rates of 20, 40, 60, 80, 100, and 120 mV / s. Double-layer capacitor (C dl The calculation formula is: ; Among them: I a Represents the anode current (mA), I b represents the cathode current (mA), and v represents the scan rate (mV / s).

[0035] Electrochemical oxidation test: Using Re-doped Ti4O7 anode sample as the anode and stainless steel electrode as the cathode, and 50 mM sodium sulfate solution as the electrolyte, oxalic acid (50 mg / L), salicylic acid (50 mg / L), coumarin (200 mg / L), and perfluorooctanoic acid (PFOA) (50 mg / L) were added respectively, at 20 mA / cm². 2 Electrochemical oxidation experiments were conducted at current density, and samples were taken at regular intervals for testing and recording. The test results were measured as the rate of organic matter degradation. Defluorination rate testing: The defluorination rate is calculated based on a series of formulas. in, Fluoride ion concentration (mg / L); The initial concentration of F in perfluorooctanoic acid (mg / L).

[0036] The test results are shown in Table 1 below.

[0037] Table 1. Test data of Re-doped Ti4O7 anode performance. Conclusion: The Re-doped Ti4O7 anode prepared by this invention can reduce the interfacial electron transfer resistance of Ti4O7, promote the direct electron transfer process, and increase the ·OH production, thereby improving the catalytic activity of the Re-doped Ti4O7 anode and its electro-oxidative degradation performance of organic pollutants such as perfluorooctanoic acid.

[0038] In Comparative Example 1, Re was not doped into the Ti4O7 anode. During the electrochemical oxidation process, the degradation of oxalic acid mainly relies on direct electron transfer, and its degradation rate reflects the electrode's direct electron transfer capability. The degradation of salicylic acid and coumarin mainly relies on hydroxyl radical-mediated indirect oxidation, and their degradation rates reflect the electrode's ·OH generation capability. Compared with the examples, the electrode prepared in Comparative Example 1 showed significantly reduced direct electron transfer capability and ·OH generation capability, thereby reducing the electrochemical degradation performance of perfluorooctanoic acid by the Ti4O7 anode.

[0039] In Comparative Example 2, Ti4O7 anodes were prepared using conventional high-temperature and high-pressure sintering processes. Compared with spark plasma sintering, the grains tend to coarsen, which reduces the electrochemical surface activity of the electrode and thus reduces the electro-oxidative degradation performance of Ti4O7 anodes for perfluorooctanoic acid.

[0040] In Comparative Example 3, the Ti4O7 anode was directly treated with carbon nanotubes. Although the carbon nanotubes improved the surface active sites and conductivity of the Ti4O7 anode, and enhanced the direct electron transfer capability and ·OH production capability of the electrode, the carbon nanotubes had poor corrosion resistance in fluorochemical wastewater and were easy to fall off, thus affecting the electro-oxidative degradation performance of the Ti4O7 anode for perfluorooctanoic acid.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a Re-doped Ti4O7 anode, characterized in that: Includes the following steps: S1: Add ammonium perrhenate solution to tetrabutyl titanate solution, add aqueous ethanol solution, continue stirring, let stand, and obtain gel; S2: The gel is dried, ground into powder, and calcined to obtain Re-doped TiO2; S3: Add Re-doped TiO2 and carbon black to anhydrous ethanol, disperse and ball-mill, vacuum dry, and perform carbon reduction treatment to obtain Re-doped Ti4O7; S4: Re-doped Ti4O7 is subjected to discharge plasma sintering and natural cooling to obtain a Re-doped Ti4O7 anode; S5: Modified carbon nanotubes were added to deionized water, ultrasonically dispersed, and then Re-doped Ti4O7 anodes were added. The mixture was then vacuum impregnated, dried, and heat-treated to obtain a composite Re-doped Ti4O7 anode.

2. The method for preparing a Re-doped Ti4O7 anode according to claim 1, characterized in that: In step S1, the preparation process of the ammonium perrhenate solution is as follows: add the ammonium perrhenate aqueous solution to ethanol and mix evenly to obtain the ammonium perrhenate solution; the preparation process of the tetrabutyl titanate solution is as follows: add tetrabutyl titanate to ethanol and mix evenly to obtain the tetrabutyl titanate solution. In the preparation of ammonium perrhenate solution, the mass ratio of ammonium perrhenate aqueous solution to ethanol is 1:(1-10), and the rhenium content in the ammonium perrhenate aqueous solution is 0-10%. In the preparation of tetrabutyl titanate solution, the mass ratio of tetrabutyl titanate to ethanol is 1:(1-10); The ethanol-water solution is composed of ethanol and deionized water, with a mass ratio of ethanol to deionized water of (1-10):

1.

3. The method for preparing a Re-doped Ti4O7 anode according to claim 1, characterized in that: In step S1, the mass ratio of ammonium perrhenate solution, tetrabutyl titanate solution and aqueous ethanol solution is 1:1:(1-10).

4. The method for preparing a Re-doped Ti4O7 anode according to claim 1, characterized in that: In step S2, the calcination parameters are: air atmosphere, heating rate of 3-10℃ / min, maximum temperature of 500-600℃, and calcination time of 1-4h.

5. The method for preparing a Re-doped Ti4O7 anode according to claim 1, characterized in that: In step S3, the carbon reduction process parameters are as follows: the gas atmosphere is argon, the argon flow rate is 80-100 mL / min, the heating rate is 5-10℃ / min, the maximum temperature is 1000-1200℃, and the holding time is 80-160 min. The molar ratio of Re-doped TiO2 to carbon black is (4-5):

1.

6. The method for preparing a Re-doped Ti4O7 anode according to claim 1, characterized in that: In step S4, the discharge plasma sintering parameters are: sintering pressure of 3-8 MPa, heating rate of 50-60℃ / min, maximum sintering temperature of 1000-1200℃, and sintering time of 10-30 min.

7. The method for preparing a Re-doped Ti4O7 anode according to claim 1, characterized in that: In step S5, the preparation process of the modified carbon nanotubes is as follows: carbon nanotubes are placed in concentrated nitric acid and refluxed at 80-110℃ for 3-8 hours. After cooling to room temperature, they are washed and dried to obtain pretreated carbon nanotubes. Pretreated carbon nanotubes were added to deionized water, ultrasonically mixed, heated to 70-80℃, and tin chloride pentahydrate and antimony chloride were added. The mixture was stirred, and the pH was adjusted to 10 with sodium hydroxide. The mixture was washed, filtered, vacuum dried, and calcined under nitrogen protection to obtain modified carbon nanotubes.

8. The method for preparing a Re-doped Ti4O7 anode according to claim 7, characterized in that: In the preparation process of the pretreated carbon nanotubes, the mass ratio of carbon nanotubes to concentrated nitric acid is 1:(20-50); in the preparation process of the modified carbon nanotubes, the mass ratio of pretreated carbon nanotubes, tin chloride pentahydrate, and antimony chloride is 1:(3-8):(0.1-0.4).

9. The method for preparing a Re-doped Ti4O7 anode according to claim 1, characterized in that: In step S5, the vacuum impregnation time is 1-3 hours; the heat treatment parameters are as follows: the gas atmosphere is an inert gas, the heating rate is 3-10℃, the maximum temperature is 200-300℃, and the time is 1-2 hours; the mass ratio of modified carbon nanotubes to Re-doped Ti4O7 anode is 1:(10-20).

10. A Re-doped Ti4O7 anode is prepared by a method according to any one of claims 1-9.

Images